
package org.apache.solr.search;

import java.util.List;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;

/** A hash key encapsulating a query, a list of filters, and a sort
 */
public final class QueryResultKey {

    final Query query;
    final Sort sort;
    final SortField[] sfields;
    final List<Query> filters;
    final int nc_flags;  // non-comparable flags... ignored by hashCode and equals
    private final int hc;  // cached hashCode
    private static SortField[] defaultSort = new SortField[0];

    public QueryResultKey(Query query, List<Query> filters, Sort sort, int nc_flags) {
        this.query = query;
        this.sort = sort;
        this.filters = filters;
        this.nc_flags = nc_flags;

        int h = query.hashCode();

        if (filters != null) {
            for (Query filt : filters) {
                h += filters.hashCode();
            }
        }

        sfields = (this.sort != null) ? this.sort.getSort() : defaultSort;
        for (SortField sf : sfields) {
            h = h * 29 + sf.hashCode();
        }

        hc = h;
    }

    @Override
    public int hashCode() {
        return hc;
    }

    @Override
    public boolean equals(Object o) {
        if (o == this) {
            return true;
        }
        if (!(o instanceof QueryResultKey)) {
            return false;
        }
        QueryResultKey other = (QueryResultKey) o;

        // fast check of the whole hash code... most hash tables will only use
        // some of the bits, so if this is a hash collision, it's still likely
        // that the full cached hash code will be different.
        if (this.hc != other.hc) {
            return false;
        }

        // check for the thing most likely to be different (and the fastest things)
        // first.
        if (this.sfields.length != other.sfields.length) {
            return false;
        }
        if (!this.query.equals(other.query)) {
            return false;
        }
        if (!isEqual(this.filters, other.filters)) {
            return false;
        }

        for (int i = 0; i < sfields.length; i++) {
            SortField sf1 = this.sfields[i];
            SortField sf2 = other.sfields[i];
            if (!sf1.equals(sf2)) {
                return false;
            }
        }

        return true;
    }

    private static boolean isEqual(Object o1, Object o2) {
        if (o1 == o2) {
            return true;  // takes care of identity and null cases
        }
        if (o1 == null || o2 == null) {
            return false;
        }
        return o1.equals(o2);
    }
}
